Electrical coil



June 21,1960 J. G. FORD ELECTRICAL COIL Filed Aug. so, 1957 |5 Linterson Conductors Limers on Insulating Spacer I NVENTOR James G. Ford.

' ATTORNEY ELECTRICAL con.

James G. Ford, Sharon, Pa., assignor to Westinghouse ElectricCorporation, East Pittsburgh, Pa., a corporation of Pennsylvania FiledAug. 30, 1957, Ser. No. 681,405

Claims. (Cl. 336-205) The invention relates generally to electricalcoils and more particularly to transformer coils.

This application is a continuation-in-part of application Serial Number424,105, now abandoned, James G. Ford, entitled Layer Insulation forDistribution Trans formers, filed April 19, 1954, and assigned to theassignee of the present application.

In the art a number of methods have been adopted for holding oranchoring the turns of an electrical coil to .resist movement whensubjected to the flow of current and electromagnetic forces tending tomove them out of position. A commonly practiced method is to cement theturns of the coil to the layer insulation by the use of resinousadhesives. This method has not been entirely satisfactory since byfilling the coil with such resinous materials it is rendered imperviousot the penetration of .oil which is essential to the building up of highimpulse strength in transformers.

An object of the invention is to provide an electrical coil, the turnsof which are so anchored as to offer high resistance to displacementwhen subjected to high electromagnetic stresses.

Another object of the present invention is to provide for preventinglateral movement of the turns of an electrical coil by providing ridgeson the layer insulation which serve as obstructions to prevent lateralmovement of the turns of the coil. m

It is also an object of the invention to prevent movement of the turnsof a coil by providing means which anchor the turns of the coil to thelayer insulation but which does not present 'an' impervious mass whichprohibits the penetration of oil into the coil.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises an article of manufacture possessingthe features, properties and the relation of elements which will beexemplified in the arpanying drawing, in which:

Figure 1 is a view in side elevation of a transformer with a portion cutaway to show a coil embodying the invention as it is mounted andimmersed in oil;

Fig. 2. is a view in section of a coil constructed in accordance withthe teachings of this invention;

Fig. 3 is a view in side elevation of a portion of a coil with parts cutaway to show details of the structure of a coil embodying the featuresof the invention; and

Fig. 4 is an enlarged view in section of a coil showing generally how itis constructed.

Referring now to Fig. l, a coil shown generally at is disposed in atransformer case 11 and immersed in a dielectric liquid 12. Theconstruction of the coil will be described in detail hereinafter and thefunction of the dielectric liquid will appear as the descriptionproceeds.

United States Patent 0 2 ,942,217 Patented June 21, 1960 In thestructure shown in Fig. 2, a tube or support 13 is provided for theturns of the coil. The tube 13 may be manufactured in accordance withthe general practice in the art. For example, a tube of pressboard, thelayers of which are bonded together by polyvinyl alcohol, is quitesatisfactory. Satisfactory tubes may also be made by scarfing the endsof a sheet of solid pressboard and then joining the scarfed ends by asuitable adhesive such as polyvinyl alcohol, cellulose acetate or aphenolic resin. However, for some types of apparatus the coil may bewound without any supporting tube or form.

The first step in building the coil involves applying to the tube orsupport 13 a sheet of layer insulation 14. This layer insulation isusually kraft paper treated to give it the desired physical andelectrical characteristics based on the design requirements. The methodsfor applying such layer insulation to a tube or support are well knownin the art and need not be detailed in this specification.

The layer insulation may be made in different ways. It has been foundsatisfactory to make it as a continuous sheet which, after or during theprocessing, is wound into a roll. When it is to be used, it is cut intoindividual sheets of the proper size and applied as layer insulation inthe making of a coil.

Another method that has proved satisfactory in the practicing of thisinvention is to apply layers of kraft paper during the coil windingoperation. In this method, after a layer of kraft paper has beenapplied, soft paper or linters, which will be described hereinafter,will be superimposed on the layer of kraft paper and bonded thereto.This operation is followed by a layer of turns ofthe conductor.

In order to meet manufacturing requirements the insulating material maybe prepared and supplied to shops either in rolls or sheets. A longnarrow sheet wound into a roll is convenient for handling.

In preparing the insulating material a sheet of kraft paper has appliedthereto a coat of an adhesive, such as shellac, phenol aldehyde typeresin, melamine resin, oleo resin, or any other oil insoluble resinknown in the art. In applying these resins, the common practice is tofirst dissolve in a suitable solvent the particular resin or resins tobe. utilized. In the case of shellac, alcohol will be employed as thesolvent; a phenol aldehyde type resin will be dissolvedin a mixture ofalcohol and aromatic hydrocarbon, such as benzene or toluene.

In the preparation of the insulating material after the adhesive, suchas a suitable resin dissolved in the solvent, has been applied to thekraft paper, and While still soft or in a sticky state, cotton lintersor some other suitable shredded fibrous material is applied anddistributed evenly over the adhesive surface. A well known methodsuitable for this operation is to deliver linters or fibrous materialsto the adhesive surface by means of an air stream flowing through anozzle. It will be readily appreciated that if the adhesive is in asticky or tacky condition, the fibers will adhere and will be bonded tothe paper when the resin dries.

Linters or other fibers applied to the adhesive surface in this mannerwill be in a random arrangement. Many of the linters or other fiberswill be only in part contact with the adhesive and will, thus, stand onend and at different angles to the surface of the paper. When theadhesive has been dried, the product will comprise a sheet of kraftpaper with a layer or mat of linters or fibers firmly bonded to it. Inworking with this material, it has been found that linters or fibers ofa length of from of an inch to of an inch, properly bonded to a sheet ofkraft paper, is quite satisfactory, and good results have been obtainedin building coils withsuch material.

Satisfactory layer insulation, which also is in accordance with theteachings of this invention, may be made by laminating a sheet of kraftpaper and a sheet of soft paper such, for example, as the soft paperfrom which Kleenex is made. Other soft papers, similar to the paper fromwhich the well-known Kleenex is made, may also be used. It will bereadilyappreciated that there are a number of such papers.

The manufacture of insulating sheet by the process of laminating a sheetof kraft or similar paper and a sheet of soft paper, such as that fromwhich Kleenex is made, may be practiced in a variety of ways. The kraftpapers and the soft paper may both be employed as long continuoussheets, and the product wound onto a roll. Of course, in some instances,it may be desirable to laminate the kraft paper and the soft paper insmall pieces, depending on the requirements of the operation in which itis to be employed.

In laminating kraft paper and soft paper, the laminating may be effectedwhen the solution of resin is applied to either sheet, preferably thekraft paper, and the two brought together when the resin is in a tackyor sticky condition. Good success in bonding the kraft paper and thesoft paper may also be effectedwhen the resin is in a thermoplasticstate after the evaporation of the Solvent.

It is preferable in the laminating process to passthe two sheets afterthe adhesive has been, applied between pressure rolls. In order to helpthe laminating procedure, the application of some heat may give goodresults. It has been foundthat when heat is applied in the laminatingprocedure, the material produced is less likely to delaminate at thetemperatures at which coils are utilized in service.

The preparation of the insulating material in rolls is desirable forplants where automatic machines are employed for cutting it into sheetsor pieces of the required size for the manufacture of coils. In thisway, the machines can be set to cut a large number of pieces of thedesired size for the making of coils of predetermined design.

While the foregoing procedure is preferable in the making of coils inmanufacturing plants where automatic machines are utilized, the lintersmay be'applied in other ways. In applying the linters to the kraft paperin the process of winding the coil, the procedure adopted will besomewhatdiife'rent.

In applying the linters in the making of the coil, an adhesive will beapplied to the tube 13. A layer of kraft paper 14 is then applied to thetube 13. -After "the layer of k'raft paper is firmly in position, anadhesive layer, such as described hereinbefore, is applied to the sheet14 by means of a brush or spray or some other method well known in theart; care being observed to prevent the application of an excessiveamount of adhesive. Linters are then applied to the adhesive layer insome well-known manner. The most usual practice is to discharge thelinters through a nozzle by the use of compressed air. In theapplication of the linters, they should be evenly distributed to form asoft mass on the kraft paper.

In some instances, it may be desirable to coat the linters after theyhave been applied with a light spray of suitable varnish or solution ofresin. In this manner, a bonded spongy mat is formed on the kraft paper.The resins in solution described hereinbefore can be employed for thisspray to be applied to the linters.

After the linters have been impregnated with a suit- :able resinousmaterial, a conductor 16 is wound on the mat carried by the kraft paper.The turns of the conductor 16 are applied under some tension, so as toform a layer of turns completely across the insulating material 14. Thewinding conductor, under a certain tension, forms grooves 17 in the matof the linters, and ridges 18 appear between the turns of the layer.

The linters applied in this procedure of winding a coil will preferablybe of the same length as linters employed in the embodiment of theinvention described for use in a plant having automatic machines. Ofcourse, when the linters are applied in this manner, they will be in arandom arrangement as hereinbefore de scribed.

It has been found that the linters or fibers which more or less stand onend arrange themselves to extend between the turns of the coil. Whensuch a mat of linters or fibers has been impregnated with the resins insolution, the linters or fibers bond themselves to the turns 16 of thelayer of turns. Therefore, when the resinous material from which the matof linters 15 is impregnated hardens, the turns 16 of the coil will beanchored to the layer of kraft paper or layer of insulation 14. Further,the hard ridges 18 formed between the turns of the layer of turns willresist lateral movement of the turns.

The composite insulation of kraft paper, either with attached linters orlaminated with soft paper, can be used either with or without resinimpregnation. In either case, grooves are formed in the soft paper, asshown at 17, with resulting ridges 18 between the turns of the conductor16. Where the soft paper is previously impregnated with a suitableresin, greater strength and greater resistance to lateral movement ofthe conductors is obtained.

The foregoing describes methods of "forming a matted insulation in whichthe conductor 16 can be readily {embedded. The mat of linters or fibersis supported by 'a layer of kraft paper of a suitable dielectricstrength. In Winding the coil, successive layers of the conductor 16 andthe layer material 14 are built up to give the-required number ofcomplete turns for a coil designed to meet predetermined requirements.

It has been found for some purposes when it is desired to rigidly anchorthe turns of the coil that it is desirable to apply a mat of linters orsoft fibrous mater'ialto both sides of the sheet of layer insulation.When a mat of linters or the equivalent in other fibrous materialsl' hasbeen applied to the side of the sheet 14 to be applied to the layer ofturns of the conductor 16, and the next layer of turns are applied, itwill press the mat of softfibers or the equivalent into position betweenthe turns of the conductor 16. As pointed out above, the mat of linterscan be impregnated with resin if desired. In the ca'se o'f a mat oflinters applied to the inner face of the sheet 14 of layer insulation,the standing linters referred to hereinbefore will project between theturns of the conductor 16. If a resinous material is employed forimpregnating the mat when it has hardened, ridges 18' will be formedbetween the turns of the conductor 16. In this matter the "turns of thefirst layer of the coil -10will be-firmly anchored in their respectivepositions and will resist movement even when subjected to strongelectromagnetic forces.

The ends of the sheets 14 of the layer insulation will be folded into aV-shape as shown at 19. These V-sha'ped members will be bonded with thelin'te'rs or equivalent fibrous material employed for making the matsand together with the ridges formed on the mats will give a very rigidmounting of the end turns of the coil. Additional strength can beobtained at the coil edges by applying a coating of varnish to thecrimped sections 19.

When the required number of layers of turns have been applied, a sheetof layer insulation 14' having a mat 'on only one side will besuperimposed on the 'coil with the mat facing inwardly. Of course, it isto be understood that this last sheet of layer insulation couldbeapplied without any mat since the next layer below will have a mat whichfunctions to, anchor the turns of the conductor 1o. After an adequatenumber of layers of turns have been built up, a tube or other protectivemeans 20 may be applied.

Nothing has been said about the size of the conductor 16 employed but itwill be readily understood that the size of conductor will depend on thespecification cf the coil and the duties which it has to perform.

The materials and turns of the conductor 16 have been so selected .andarranged that the dielectric 12 may readily penetrate the coil.Therefore in the case of transformers and other similar apparatus highimpulse strength will be displayed when put in test or use.

Although the soft mat of material or linters have been referred tohereinbefore as being pervious to oil, it is within the scope of thisinvention to use material for the soft mat or use linters which are notpervious to oil. One such type of material is known in the art as glassfibers. It is also contemplated that coils of the type described hereincould be used in dry type apparatus, such as air cooled or drytransformers, wherein the soft mat of material or limiters would not beexposed to oil.

Since certain changes in carrying out the above process, and certainmodifications in the article which embody the invention may be madewithout departing from its scope, it is intended that all mattercontained in the above description or shown in the accompanying drawingshall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In an electrical coil for electrical apparatus in combination, asupport, a layer of insulating material carried by the support, a layerof linters applied to the layer of insulating material to form a mat,the ends of the linters extending upwardly, a resinous material appliedto the linters and layer of insulating material, the resinous materialbeing capable of bonding the linters to one another and to the layer ofinsulating material and of hardening, a plurality of turns of aconductor applied to the mat of linters partially embedding themselvesin the mat, and ridges formed by the bonding material and the lintersbetween the conductors, the upwardly extending ends of the linters beingalso bonded to the turns of the conductor, the ridges and the ends ofthe linters cooperating to oppose lateral movement of the turns of theconductor under stress.

2. In an electrical coil for electrical apparatus in combination, acylindrical support, a layer of insulating material wound on thecylindrical support, a soft fibrous shredded material capable ofdistortion applied to the layer of insulating material forming a mat, aresinous material capable of hardening and bonding applied to the matand layer of insulating material, a plurality of turns of a conductor sowound on the mat that the turns partially embed themselves therein, theends of the shredded material extending upwardly between the turns ofthe conductor and ridges formed from the mat and bonding material whichextends upwardly between the turns of the conductor, the bondingmaterial bonding the upwardly extending ends of the shredded material tothe turns of the conductor, the ridges and bonded ends of the upwardlyextending shredded material cooperating to oppose lateral movement ofthe turns of the conductor when subjected to stresses by the flow ofelectrical current.

3. In an electrical coil for electrical apparatus in combination, acylindrical support, a layer of insulating material carried by thesupport, a layer of linters applied to the layer of insulating materialforming a soft mat, a resinous material capable of hardening and ofbonding applied to the mat of linters and the layer of insulatingmaterial, the ends of the linters projecting upwardly between the turnsof the conductor, the bonding material bonding the ends of the lintersto the turns of the conducting material, and ridges formed from thebonding material when hardened and the linters coated with the bondingmaterial, the ridges and the ends of the linters bonded to the turns ofthe conductor cooperating to hold the turns of the conductor againstlateral movement, the edges of the layer of insulating material beingfolded at the ends of the coil to cooperate in retaining the turns ofthe coil in position.

4. In an electrical coil for electrical apparatus in combination, acylindrical support, a layer of insulating material applied to thecylindrical support, a mass of linters applied to the layer ofinsulating material to form a soft material, a resinous material bondingthe linters to one another and to the layer of insulating material, aplurality of turns of the conductor wound on the mass of linters, theconductors partially embedding themselves in the mat, the ends of thelinters extending upwardly between the conductors, ridges formed betweenthe conductors by the resinous material and linters, the resinousmaterial serving to bond the ends of the linters extending upwardlybetween the turns of the conductor to the turns, the ridges and ends ofthe linters when the resinous material has hardened cooperating tooppose lateral movement of the turns of the conductor, a second layer ofinsulating material having linters bonded thereto to form a mat appliedover the plurality of turns of the conductor, the second layer ofinsulating material carrying the mat of linters being applied withsufficient pressure to form, from the mat of linters and resinousmaterial ridges between the plurality of turns of the conductor, theridges formed on the opposed layers of insulating material and the endsof the linters bonded to the turns of the conductor cooperating tooppose lateral movement of the turns of the conductor when subjected tostresses caused by the flow of electrical current.

5. In an electrical coil for electrical apparatus in combination, asupport, a plurality of layers of insulating material having a mass oflinters applied thereto to form relatively soft mats and a plurality oflayers of turns of a conductor applied alternately with the layers ofinsulation, a resinous material capable of bonding and hardening, theresinous material bonding mats of linters to the layers of insulationand to the layers of turns of the conductor, the ends of the lintersextending between the turns of the conductor, the layers of the turns ofthe conductor and the layers of insulating material being sosuperimposed on one another that the turns of the conductor are embeddedin the applied mats of linters, ridges formed in the mats carried by thelayers of insulation, the ridges and the ends of the linters projectingbetween the turns of the conductors cooperating when the resinousmaterial has hardened to resist the lateral movement of the turns of theconductor when subjected to stress by electrical current flowingtherethrough.

References Cited in the file of this patent UNITED STATES PATENTS673,521 Heany May 7, 1901 1,840,139 Turner Jan. 5, 1932 1,975,620 SaulOct. 2, 1934 1,998,827 Worrell et al Apr. 23, 1935 2,172,445 Lutz Sept.12, 1939 2,246,159 Work et a1. June 17, 1941

